Exhaust gas exhausted from an internal combustion engine includes a toxic substance such as nitrogen oxide, carbon hydride, or carbon monoxide. Accordingly, an exhaust purification device purifying the exhaust gas is generally mounted in a vehicle that moves using a driving force generated by the internal combustion engine.
The exhaust purification device has a three-way catalytic agent. The three-way catalytic agent renders the toxic substance harmless by an oxidation reaction and a reduction reaction using a catalyst. The catalyst comes in an active state that causes the oxidation reaction and the reduction reaction when being heated by a heat of the exhaust gas and having a high temperature.
In recent years, exhaust particulates included in the exhaust gas are required to be reduced in addition to rendering nitrogen oxide etc. included in the exhaust gas harmless. In order to reduce the exhaust particulates, an air-fuel ratio in cylinders of the internal combustion engine may be controlled to reduce a generation amount of the exhaust particulates. However, the exhaust particulates are desired to be reduced in quantity in addition to in weight, and therefore reducing the generation amount is not sufficient.
Then, Patent Literature 1 discloses an exhaust purification device that has, in addition to the three-way catalytic agent, a particulate filter that is arranged in an exhaust passage and collects the exhaust particulates. The particular filter suppresses an emission of the exhaust particulates included in the exhaust gas to outside.
An amount of the exhaust particulates accumulated in the particulate filter increases as time elapses. According to the exhaust purification device disclosed in Patent Literature 1, the exhaust particulates accumulated in the particulate filter are burnt to be removed from the particulate filter, such that the particulate filter is prevented from being clogged. In addition, the particulate filter is arranged upstream of the three-way catalytic agent (i.e., on a side adjacent to the internal combustion engine) such that the exhaust gas, which has a high temperature for burning the exhaust particulates, is supplied to the particulate filter.